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Model Forum / Radio Controlled / Water Models / April 2005motor shaft water proof
Can you tell me how to prevent water going in through the drive shaft? This will be under water line and submersible area. Is there any special water proof bearing available? Or I can buy a motor that already have this buildin? Thank you? >Can you tell me how to prevent water going in through the drive shaft? >This will be under water line and submersible area. >Is there any special water proof bearing available? >Or I can buy a motor that already have this buildin? >Thank you? There are several sources of pre-built stuffing tubes. Usually, any source that has props also has stuffing tubes. They're also pretty easy to build - here's my favorite method: http://www.jkmiller.net/ntxbg/pgOnTheWays/pgStuffTube.htm JM > Can you tell me how to prevent water going in through the drive shaft? > This will be under water line and submersible area. > Is there any special water proof bearing available? > Or I can buy a motor that already have this buildin? > Thank you? I'm not a boat person but someone hanging around for Homelite information but..... If the drive shaft is running below waterline isn't there a mechanism similar to the oil slinger grooves found on crankshafts and/or their seals? These are usually near invisible grooves that get overlooked by many engine builders (automotive in this case). With these types of seals and oil slingers as long as the shaft is spinning the small grooves will push any seapage to one side of the seal (in this case outside). Considering this will hold back oil seepage at 60+psi I'm sure that water wouldn't be a problem if the design was right.  SignatureThe Raven http://www.80scartoons.co.uk/batfinkquote.mp3 ** Now I will bring chaos to the world! How to design the dripless shaftseals? Any reference material? Thanks. > I'm not a boat person but someone hanging around for Homelite information > but..... [quoted text clipped - 12 lines] > http://www.80scartoons.co.uk/batfinkquote.mp3 > ** Now I will bring chaos to the world! > How to design the dripless shaftseals? Any reference material? Thanks. > [quoted text clipped - 20 lines] >>http://www.80scartoons.co.uk/batfinkquote.mp3 >>** Now I will bring chaos to the world! Well, there was a good article on that topic in the German magazine O&P, a professional magazine for engineers in the fields of oilhydraulics and pneumatics (I happen to work in this field). The article was published between 15 and 20 years ago, so it will be hard to find. The essence as I recall was, that the shape of the seal lip, is what really counts, it has to have different angles on the inside (flat) and outside (steep). The different angles create different distributions of shear stress in the fluid, and that creates a small pressure difference from outside to inside, causing a small flow. The short form is: The seal doesn't seal, it pumps. That's why you must mount it the right way around, and you better not operate your car engine under water or you'll have water in the engine. Truck axles, by the way, have special shaft seals which seal both ways. I once designed a tandem pump for 2 different fluids, and after learning it the hard way, I put in 2 shaft seals between both pumps and a vent in between. So, always use your shaft seal the right way around, direction of shaft speed doesn't matter. |
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